Remote communication devices, radio frequency identification devices, wireless communication systems, wireless communication methods, radio frequency identification device communication methods, and methods of forming a remote communication device

ABSTRACT

Remote communication devices, radio frequency identification devices, wireless communication systems, wireless communication methods, radio frequency identification device communication methods, and methods of forming a remote intelligent communication device are provided. According to one aspect, a remote intelligent communication device includes communication circuitry configured to at least one of receive communication signals and generate communication signals; and an antenna coupled with the communication circuitry and substantially tuned to a plurality of frequencies, the antenna being configured to communicate wireless signals corresponding to the communication signals including at least one of receiving wireless signals and outputting wireless signals. Another aspect includes a wireless communication method including providing a remote intelligent communication device having an antenna substantially tuned to a plurality of frequencies; and communicating wireless signals using the antenna including at least one of receiving wireless signals at one of the frequencies and outputting wireless signals at one of the frequencies.

RELATED PATENT DATA

This patent resulted from a continuation application of and claimspriority to U.S. patent application Ser. No. 10/791,187, filed Mar. 1,2004, entitled “Remote Communication Devices, Radio FrequencyIdentification Devices, Wireless Communication Systems, WirelessCommunication Methods, Radio Frequency Identification DeviceCommunication Methods, and Methods of Forming a Remote CommunicationDevice”, naming Freddie W. Smith and Dirgha Khatri as inventors, whichresulted from a continuation application of U.S. patent application Ser.No. 09/389,534, filed Sep. 2, 1999, now abandoned entitled “RemoteCommunication Devices, Radio Frequency Identification Devices, WirelessCommunication Systems, Wireless Communication Methods, Radio FrequencyIdentification Device Communication Methods, and Methods of Forming aRemote Communication Device”, naming Freddie W. Smith and Dirgha Khatrias inventors, the disclosures of which is incorporated by reference.

TECHNICAL FIELD

The present invention relates to remote communication devices, radiofrequency identification devices, wireless communication systems,wireless communication methods, radio frequency identification devicecommunication methods, and methods of forming a remote communicationdevice.

BACKGROUND OF THE INVENTION

Electronic identification systems typically comprise two devices whichare configured to communicate with one another. Preferred configurationsof the electronic identification systems are operable to provide suchcommunications via a wireless medium.

One such configuration is described in U.S. patent application Ser. No.08/705,043, filed Aug. 29, 1996, assigned to the assignee of the presentapplication, and incorporated herein by reference. This applicationdiscloses the use of a radio frequency (RF) communication systemincluding communication devices. The disclosed communication devicesinclude an interrogator and a remote transponder, such as a tag or card.

Such communication systems can be used in various applications such asidentification applications. The interrogator is configured to output apolling or interrogation signal which may comprise a radio frequencysignal including a predefined code. The remote transponders of such acommunication system are operable to transmit an identification signalresponsive to receiving an appropriate polling or interrogation signal.

More specifically, the appropriate transponders are configured torecognize the predefined code. The transponders receiving the code cansubsequently output a particular identification signal which isassociated with the transmitting transponder. Following transmission ofthe polling signal, the interrogator is configured to receive theidentification signals enabling detection of the presence ofcorresponding transponders.

Such communication systems are useable in identification applicationssuch as inventory or other object monitoring. For example, a remoteidentification device is initially attached to an object of interest.Responsive to receiving the appropriate polling signal, theidentification device is equipped to output an identification signal.Generating the identification signal identifies the presence or locationof the identification device and the article or object attached thereto.

Some conventional electronic identification systems utilize backscattercommunication techniques. More specifically, the interrogator outputs apolling signal followed by a continuous wave (CW) signal. The remotecommunication devices are configured to modulate the continuous wavesignal in backscatter communication configurations. This modulationtypically includes selective reflection of the continuous wave signal.The reflected continuous wave signal includes the reply message from theremote devices which is demodulated by the interrogator.

SUMMARY OF THE INVENTION

The present invention relates to remote communication devices, radiofrequency identification devices, wireless communication systems,wireless communication methods, radio frequency identification devicecommunication methods, and methods of forming a remote communicationdevice.

According to one aspect of the invention, a wireless communicationsystem is provided. The wireless communication system comprises aninterrogator and one or more remote communication devices individuallyconfigured to communicate with the interrogator in at least oneembodiment. Exemplary remote communication devices include remoteintelligent communication devices or radio frequency identificationdevices (RFID).

One configuration of the remote communication device includescommunication circuitry and at least one antenna configured tocommunicate at a plurality of frequencies. The antenna is substantiallytuned to plural frequencies to implement communications. The remotecommunication device includes a transmit antenna and receive antenna inone embodiment. An exemplary transmit antenna comprises a dipole antennaand an exemplary receive antenna comprises a loop antenna. The remotecommunication device is configured for backscatter communications in atleast one arrangement.

The invention additionally provides methods and additional structuralaspects as described below.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

FIG. 1 is a functional block diagram of an exemplary communicationsystem.

FIG. 2 is a front view of a wireless remote communication deviceaccording to one embodiment of the invention.

FIG. 3 is a front view of an employee badge according to anotherembodiment of the invention.

FIG. 4 is an illustrative representation of one substrate surface of aremote communication device.

FIG. 5 is an illustrative representation of exemplary dimensions of atransmit antenna of the remote communication device.

FIG. 6 is an illustrative representation of additional exemplarydimensions of the transmit antenna.

FIG. 7 is an illustrative representation of exemplary dimensions of areceive antenna of the remote communication device.

FIG. 8 is an illustrative representation of an exemplary conductivetrace formed upon another substrate surface of the remote communicationdevice.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws “to promote the progressof science and useful arts” (Article 1, Section 8).

FIG. 1 illustrates a wireless communication system 10 embodying theinvention. Communication system 10 is configured as an electronicidentification system in the embodiment described herein. Otherapplications of communication system 10 are possible. Further, thedescribed communication system 10 is configured for backscattercommunications as described further below. Other communication protocolsare utilized in other embodiments.

The depicted communication system 10 includes at least one electronicwireless remote communication device 12 and an interrogator 26. Radiofrequency communications can occur intermediate remote communicationdevice 12 and interrogator 26 for use in identification systems andproduct monitoring systems as exemplary applications.

Devices 12 include radio frequency identification devices (RFID) orremote intelligent communication (RIC) devices in the exemplaryembodiments described herein. Remote intelligent communication devicescan perform functions in addition to identification functions. Exemplarydevices 12 are disclosed in U.S. patent application Ser. No. 08/705,043,filed Aug. 29, 1996. Plural wireless remote communication devices 12typically communicate with interrogator 26 although only one such device12 is illustrated in FIG. 1. Such a remote communication device 12 canbe referred to as a tag or card as illustrated and described below.

Although multiple remote communication devices 12 can be employed incommunication system 10, there is typically no communication betweenmultiple devices 12. Instead, the multiple communication devices 12communicate with interrogator 26. Multiple communication devices 12 canbe used in the same field of interrogator 26 (i.e., within thecommunications range of interrogator 26). Similarly, multipleinterrogators 26 can be in proximity to one or more of remotecommunication devices 12.

The above described system 10 is advantageous over prior art devicesthat utilize magnetic field effect systems because, with system 10, agreater range can be achieved, and more information can be communicated(instead of just identification information). As a result, such a system10 can be used, for example, to monitor large warehouse inventorieshaving many unique products needing individual discrimination todetermine the presence of particular items within a large lot of taggedproducts.

Remote communication device 12 is configured to interface withinterrogator 26 using a wireless medium in one embodiment. Morespecifically, communications intermediate communication device 12 andinterrogator 26 occur via an electromagnetic link, such as an RF link(e.g., at microwave frequencies) in the described embodiment.Interrogator 26 is configured to output forward link wirelesscommunications 27. Further, interrogator 26 is operable to receive replyor return link wireless communications 29 from remote communicationdevices 12 responsive to the outputting of forward link communication27.

In accordance with the above, forward link communications 27 and returnlink communications 29 individually comprise wireless signals, such asradio frequency signals, in the described embodiment. Other forms ofelectromagnetic communication, such as infrared, etc., are possible.

Interrogator unit 26 includes a plurality of antennas X1, R1, as well astransmitting and receiving circuitry, similar to that implemented indevices 12. Antenna X1 comprises a transmit antenna and antenna R1comprises a receive antenna individually connected to interrogator 26.

In operation, interrogator 26 transmits the interrogation command orforward link communication signal 27 via antenna X1. Communicationdevice 12 is operable to receive the incoming forward link signal. Uponreceiving signal 27, communication device 12 is operable to respond bycommunicating the responsive reply or return link communication signal29.

In one embodiment, responsive signal 29 is encoded with information thatuniquely identifies, or labels the particular device 12 that istransmitting, so as to identify any object, animal, automobile, person,etc., with which remote communication device 12 is associated.

More specifically, remote communication device 12 is configured tooutput an identification signal within reply link communication 29responsive to receiving forward link wireless communication 27.Interrogator 26 is configured to receive and recognize theidentification signal within the return or reply link communication 29.The identification signal can be utilized to identify the particulartransmitting communication device 12.

Referring to FIG. 2, one embodiment of remote communication device 12 isillustrated. The depicted remote communication device 12 includescommunication circuitry 16 having a receiver and a transmitter.Communication circuitry 16 may be implemented as transponder circuitryin one configuration. Exemplary communication circuitry 16 includes asmall outline integrated circuit (SOIC) 19 available as radio frequencyidentification device (RFID) circuitry from Micron Communications Inc.,3176 South Denver Way, Boise, Id. 83705 under the trademark MicroStamp™Engine and having designations MSEM256X10SG, MT59RC256R1FG-5.

Communication circuitry 16 is configured to receive and processcommunication signals. Exemplary processing includes analyzing thereceived communication signal for identification information andprocessing commands within the communication signal. More or lessprocessing can be performed by communication circuitry 16. Thereafter,communication circuitry 16 selectively generates communication signalsfor communication to interrogator 26. Remote communication device 12further includes a power source 18 connected to communication circuitry16 to supply operational power to communication circuitry 16 includingintegrated circuit 19.

Power source 18 is a thin film battery in the illustrated embodiment,however, in alternative embodiments, other forms of power sources can beemployed. If the power source 18 is a battery, the battery can take anysuitable form. Preferably, the battery type will be selected dependingon weight, size, and life requirements for a particular application. Inone embodiment, battery 18 is a thin profile button-type cell forming asmall, thin energy cell more commonly utilized in watches and smallelectronic devices requiring a thin profile. A conventional button-typecell has a pair of electrodes, an anode formed by one face and a cathodeformed by an opposite face. In an alternative embodiment, the batterycomprises a series connected pair of button type cells.

Communication device 12 further includes at least one antenna connectedto communication circuitry 16 and configured for at least one ofwireless transmission and reception. In the illustrated embodiment,communication device 12 includes at least one receive antenna 44connected to communication circuitry 16 for radio frequency reception bycommunication circuitry 16, and at least one transmit antenna 46connected to communication circuitry 16 for radio frequency transmissionby communication circuitry 16.

Receive antenna 44 is configured to receive forward wireless signals 27and apply communication signals corresponding to the received wirelesssignals to communication circuitry 16. Transmit antenna 46 is configuredto receive generated communication signals from communication circuitry16 and output remote wireless signals 29 corresponding to the generatedcommunication signals. The described antennas are implemented as printedmicrostrip antennas in one configuration. Further, receive antenna 44comprises a loop antenna and the transmit antenna 46 comprises a dipoleantenna in the described configuration. Transmit antenna 46 has pluraldipole halves 47, 48 in the configuration illustrated in FIG. 4.

Communication device 12 can be included in any appropriate housing orpackaging. FIG. 2 shows but one example of a housing in the form of aminiature housing 11 encasing device 12 to define a tag which can besupported by an object (e.g., hung from an object, affixed to an object,etc.).

Referring to FIG. 3, an alternative configuration of remotecommunication device 12 a is illustrated. FIG. 3 shows remotecommunication device 12 a having a housing 11 a in the form of a card.Card housing 11 a preferably comprises plastic or other suitablematerial. Remote communication device 12 a may be utilized as anemployee identification badge including the communication circuitry 16.In one embodiment, the front face of housing 11 a has visualidentification features such as an employee photograph or a fingerprintin addition to identifying text.

Although two particular types of housings have been disclosed, thecommunication device 12 can be included in any appropriate housing.Communication device 12 is preferably of a small size that lends itselfto applications employing small housings, such as cards, miniature tags,etc. Larger housings can also be employed. The communication device 12,provided in any appropriate housing, can be supported from or attachedto an object in any desired manner.

Referring to FIG. 4, further details of one configuration of remotecommunication device 12 are shown. The illustrated remote communicationdevice 12 includes a substrate 50 having plural surfaces (surface 52 isshown in FIG. 4). The illustrated substrate 50 has exemplary dimensionsincluding a length l of 60 mm and a width w of 53 mm.

In the described configuration of remote communication device 12,substrate 50 comprises FR4 board. Conductive traces 53 are provided uponsurface 52 of substrate 50 to form desired circuitry includinginterconnections, antennas, etc. Such traces 53 can be formed by etchingcopper cladding provided upon surface 52.

As shown, conductive traces 53 include receive antenna 44 and transmitantenna 46 individually formed upon surface 52. In addition, traces 53include power source connections for coupling with power source 18(shown in phantom in FIG. 3). More specifically, power sourceconnections include a positive voltage connection 54 and a negativevoltage connection 56 as shown.

A negative terminal of power source 18 may be electrically coupleddirectly with negative connection 56. In the described configuration,power source 18 is seated upon and coupled directly above negativeconnection 56.

An elevated support connection 58 is formed elevationally above powersource 18 and substrate surface 52. Elevated support connection 58 iscoupled with a positive terminal of power source 18. The positiveterminal can be opposite the negative terminal of power source 18 whichis coupled with negative connector 56. Plural conductive posts 60 areprovided to couple elevated support connection 58 with positiveconnection 54.

A via connection 62 is shown formed through substrate 50. Via connection62 provides coupling of negative connection 56 formed upon surface 52 toan opposing surface of substrate 50 shown in FIG. 8. Via connection 62can provide coupling to a ground plane formed upon the opposing surfaceas described below in further detail. Positive connection 54 couplesconductive posts 60 with receive antenna 44 and a pin 3 (positivevoltage input) of integrated circuit 19. Antenna 44 is additionallycoupled with a pin 7 (RX input) of integrated circuit 19 as shown.

Conductive traces 53 formed upon surface 52 also couple communicationcircuitry 16 and a capacitor 64 with other circuitry as illustrated.Capacitor 64 is coupled with one lead of receive antenna 44 and a viaconnection 66. Via connection 66 provides electrical coupling ofcapacitor 64 with a ground connection upon the opposing surface ofsubstrate 50. Accordingly, capacitor 64 operates to provide coupling ofpositive connection 54 with the ground reference voltage of power source18. Capacitor 64 is a 0.1 microfarad capacitor in the describedembodiment sufficient to provide static discharge protection.

The formed conductive traces 53 also operate to couple the lead ofreceive antenna 44 with pin 7 of integrated circuit 19. Pins 5, 6 ofintegrated circuit 19 are coupled with respective via connections 68,69. Via connections 68, 69 provide electrical connection throughsubstrate 50 to a transmission line described with reference to FIG. 8.Via connections 71, 73 are coupled with opposite ends of thetransmission line and dipole halves 47, 48 of transmit antenna 46.Integrated circuit 19 is electrically coupled with a plurality of pinconnections 67 of conductive traces 53. Plural pins 9, 13-16 ofintegrated circuit 19 are coupled with a via connection 74 which iscoupled through the ground plane to the negative terminal of powersource 18.

In the illustrated configuration including power source 18 withinreceive antenna 44, receive antenna 44 is tuned to a first frequency(approximately 915 MHz in the described embodiment). Power source 18provides capacitive loading which assists with tuning of antenna 44 tothe desired frequency.

Receive antenna 44 further includes an impedance reduction strip 70provided in a substantially rectangular configuration in the depictedembodiment. Other configurations of impedance reduction strip 70 arepossible. Impedance reduction strip 70 comprises a conductor whichoperates to effectively lower the impedance of receive antenna 44 andprovide enhanced operation of antenna 44 at another higher frequency(e.g., 2.45 GHz) without excessive degradation of communication at thefirst frequency (e.g., 915 MHz).

Thus, with impedance reduction strip 70, receive antenna 44 issubstantially tuned to a plurality of independent frequency bandsindividually having a bandwidth of approximately twenty percent of thehighest center frequency (e.g., +/−200 MHz for 2.45 GHz). Receiveantenna 44 is tuned to plural exclusive non-overlapping frequency bandsin the described arrangement. Receive antenna 44 is configured tocommunicate wireless signals at a plurality of substantially resonantfrequencies. More specifically, the illustrated configuration of receiveantenna 44 can electromagnetically communicate with a return loss ofless than or equal to approximately −9 dB at the plural frequencies.

The illustrated configuration of transit antenna 46 includes pluralvertical portions and horizontal portions. More specifically, dipolehalf 47 includes a vertical portion 80 and a horizontal portion 82.Dipole half 48 includes a vertical portion 84 and a horizontal portion86.

Additionally, transmit antenna 46 includes an impedance reduction strip72 formed in one exemplary configuration as illustrated in FIG. 4.Impedance reduction strip 72 is a conductor formed adjacent one of theleads of transmit antenna 46. Impedance reduction strip 72 operates toreduce the impedance of dipole half 48 of transmit antenna 46 in thedepicted configuration. Other arrangements for impedance reduction strip72 are possible.

The illustrated transmit antenna 46 is configured to communicatewireless signals at a plurality of substantially resonant frequencies.Transmit antenna 46 is substantially tuned to a plurality of independentfrequency bands individually having a bandwidth of approximately twentypercent of the highest center frequency. Transmit antenna 46 is tuned toplural exclusive non-overlapping frequency bands in the describedarrangement.

For example, the depicted transmit antenna 46 is substantially tuned to915 MHz and 2.45 GHz. Horizontal portions 82, 86 of transmit antenna 46are tuned to substantially communicate at a first frequency (e.g., 2.45GHz communications). Vertical portions 80, 84 of transmit antenna 46 incombination with horizontal portions 82, 86 are tuned to providecommunications at a second frequency (e.g., 915 MHz) with horizontalportions 82, 86. Transmit antenna 46 is configured toelectromagnetically communicate with a return loss of less than or equalto approximately −9 dB at the plurality of frequencies. Provision ofimpedance reduction strip 72 operates to improve tuning of transmitantenna 46 to the plural independent frequency bands.

Interrogator 26 (shown in FIG. 1) is configured to communicate at one ormore of a plurality of frequencies. The frequency of communicationintermediate interrogator 26 and remote communication device 12 isgenerally controlled by interrogator 26. For example, in someapplications, a 915 MHz frequency may be desirable for longer rangecommunications while in other applications a 2.45 GHz frequency mayprovide advantageous benefits (e.g., severe interference may beexperienced in another one of the frequency bands). Interrogator 26outputs forward signals 27 at the desired frequency or frequencies.

Thereafter, interrogator 26 outputs a continuous wave signal at one ormore of the frequencies. Remote communication device 12 selectivelymodulates a received continuous wave signal during backscattercommunications. Accordingly, the modulated backscatter return signal isprovided at the original frequency of the continuous wave signaloutputted by interrogator 26. Thus, in the described embodiment, thefrequency of communication of remote communication device 12 isdetermined responsive to a frequency of communication of interrogator26. Other communication methods may be utilized.

Referring to FIGS. 5-7, exemplary dimensions of receive antenna 44 andtransmit antenna 46 formed upon surface 52 are illustrated. Referringspecifically to FIG. 5, dipole half 47 of transmit antenna 46 is shown.Vertical portion 80 of dipole half 47 has a thickness a of 2.3 mm.Vertical portion 80 additionally includes a length b of 55 mm.Horizontal portion 82 has a length c of 22.3 mm. Horizontal portion 82additionally includes a width d of 3 mm.

Referring to FIG. 6, details of dipole half 48 are shown. Dipole half 48includes a vertical portion 84 and a horizontal portion 86 adjacentimpedance reduction strip 72. Vertical portion 84 has an equivalentwidth and length to that of vertical portion 80 of antenna half 47.Further, horizontal portion 86 has a length equivalent to that ofhorizontal portion 82 of antenna half 47. A dimension g including thewidth of horizontal portion 86 and the width of impedance reductionstrip 72 is 7.73 mm. Another dimension h including a reduced width ofimpedance reduction strip 72 and horizontal portion 86 is 5 mm. Further,a dimension i corresponding to one length of impedance reduction strip72 is 17 mm. The depicted dimensions correspond to one configuration oftransmit antenna 46 of remote communication device 12. Otherconfigurations are possible.

Referring to FIG. 7, exemplary dimensions of receive antenna 44 areshown. Receive antenna 44 includes horizontal portions 88-90. Inaddition, receive antenna 44 includes vertical portions 92, 93.Horizontal portions 88, 89 individually have a length corresponding to adimension m of 14.7 mm. Individual antenna portions 88-90, 92, 93individually have a width corresponding to dimension n of 1.35 mm.Vertical portions 92, 93 individually have a length o having a dimensionof 33.8 mm. Horizontal portion 90 also has a length of dimension o of33.8 mm. Impedance reduction strip 70 and horizontal portion 89 have acombined width p of 5.73 mm.

Referring to FIG. 8, a surface 55 of substrate 50 opposite surface 52described above is shown. Surface 55 of substrate 50 includes conductivetraces 57 formed as shown in the described embodiment. Conductive traces57 can comprise etched copper cladding in an FR4 board configuration.

The depicted conductive trace 57 includes a ground plane 96 and atransmission line 97 comprising plural conductors 98, 99. Ground plane96 is coupled with negative connection 56 using via connection 62.Further, ground plane 96 is also coupled with via connections 66, 74.

Transmission line 97 comprises a quarter-wavelength transmission line inthe described embodiment. Transmission line 97 operates to couplebackscatter pins 5, 6 of integrated circuit 19 shown in FIG. 4 withrespective dipole halves 48, 47 of transmit antenna 46. Transmissionline 97 operates to provide an inverting function in accordance with thedescribed embodiment. For example, if integrated circuit 19 shortcircuits pins coupled with via connections 68, 69, an open circuit isseen at via connections 71, 73 coupled with antenna halves 47, 48.Conversely, if an open circuit is provided intermediate via connections68, 69, a short circuit is seen at via connections 71, 73 for 2.45 GHzcommunications.

Various dimensions of conductive trace 57 are provided below inaccordance with an exemplary configuration. Other configurations arepossible. In the described embodiment, ground plane 96 includes a widthof dimension s of 8.44 mm. Further, ground plane 96 has a length t of 34mm. Conductors 98, 99 individually have a length corresponding todimension u of 10.5 mm. Further, individual conductors 98, 99 have awidth of 1 mm.

Provision of a remote communication device 12 as described hereinprovides improved communications at plural independent frequency bands.For example, such a remote communication device 12 has been observed tohave a forward range of approximately 170 feet and a return range ofapproximately 300 feet at 915 MHz. Further, the remote communicationdevice has been observed to have a forward range of 28 feet and a returnrange of 90 feet at 2.45 GHz.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

1. A radio frequency identification (RFID) tag comprising: a substratehaving a dipole antenna formed thereon, the dipole antenna having afirst half and a second half, the first half further having a firstshort section and a first long section, and the second half having asecond short section and a second long section; wherein the first shortsection and the second short section are configured to operate at afirst frequency; and wherein the first long section and the second longsection, in cooperation with the first short section and the secondshort section, are configured to operate at a second frequency.
 2. TheRFID tag of claim 1, further comprising: communication circuitry coupledto the dipole antenna by a quarter-wavelength transmission line.
 3. TheRFID tag of claim 2, wherein the quarter-wavelength is determined by thefirst frequency.
 4. The RFID tag of claim 1, wherein the first frequencyis higher than the second frequency.
 5. The RFID tag of claim 1, whereinthe first and second short sections are laid out on the same first edgeof the substrate, the first long section is laid out on a second edge ofthe substrate, and the second long section is laid out on a third edgeof the substrate.
 6. The RFID tag of claim 1, further comprising: animpedance reduction strip adjacent to the first short section.
 7. TheRFID tag of claim 1, wherein the second frequency provides longer rangecommunications between the RFID tag and an interrogator.
 8. The RFID tagof claim 1, further comprising: a receive antenna formed on thesubstrate.
 9. The RFID tag of claim 8, wherein the receive antenna is aloop antenna.
 10. A method of manufacturing a radio frequencyidentification (RFID) tag comprising: forming a first half of a dipoleantenna, the first half having a first short section and a first longsection, the first short section formed along a first edge of asubstrate and the first long section formed along a second edge of thesubstrate; and forming a second half of a dipole antenna, the secondhalf having a second short section and a second long section, the secondshort section formed along the first edge of the substrate and thesecond long section formed along a third edge of the substrate.
 11. Themethod of claim 10, wherein the second edge is opposite the third edgeon the substrate.
 12. The method of claim 10, wherein the second edgeand third edge are perpendicular to the first edge of the substrate. 13.The method of claim 10, wherein the first half and the second half areetched copper cladding on the substrate.
 14. The method of claim 10,further comprising: forming an impedance reduction strip adjacent to thefirst half.
 15. The method of claim 10, wherein the first and secondshort sections are tuned to communicate at a first frequency, andwherein the first and second long sections in combination with the firstand second short sections are tuned to communicate a second frequency.16. The method of claim 15, wherein the first frequency is higher thanthe second frequency.
 17. The method of claim 10, further comprising:forming a receive antenna on the substrate.
 18. The method of claim 17,wherein the receive antenna is a loop antenna.
 19. The method of claim10, further comprising: attaching communication circuitry to thesubstrate.
 20. The method of claim 19, further comprising: forming aquarter-wavelength transmission line on the substrate, wherein thequarter-wavelength transmission line is used to couple the communicationcircuitry to the first half and the second half of the dipole antenna.21. The method of claim 19, wherein the communication circuitry isconfigured to selectively short or isolate the first half and the secondhalf of the dipole antenna to provide backscatter communications.
 22. Acommunications system comprising: an interrogator configured to providecontinuous-wave signals in a plurality of frequency bands; and a remotecommunication device having an antenna adapted for use in both a firstfrequency band and a second frequency band separate from the firstfrequency band, wherein the remote communication device provides replysignals to the interrogator at a continuous-wave frequency selected bythe interrogator.
 23. The communications system of claim 22, wherein theinterrogator selects the continuous wave frequency based upon a desiredcommunication range.
 24. The communications system of claim 22, whereinthe interrogator selects the continuous wave frequency to avoidinterference.
 25. The communications system of claim 24, wherein theinterrogator selects the continuous wave frequency based upon a desiredcommunication range.
 26. The communications system of claim 22, whereinthe remote communications device generates the reply signals byselectively shorting and opening a connection between a first half and asecond half of the dipole antenna.
 27. The communications system ofclaim 22, wherein the remote communication device further comprises: animpedance reduction element formed adjacent to the dipole antenna.